1. Field of the Invention
The present invention relates to a method of managing recordable areas with respect to a disc-like recording medium capable of recording data such as music data. The present invention also relates to a method of recording the data in the recordable areas.
2. Description of the Background Information
There have been known data rewritable disc media capable of recording music data by a user. Such a disc medium is provided with a data area (U-TOC: USER TABLE OF CONTENTS) for managing areas in which a data such as a music data has been already recorded and recordable areas. The management data is rewritten at the termination of each action such as recording, editing, overwriting or erasing.
For example, in voice-recording a certain program, an audio-recording apparatus retrieves recordable areas on the disc by means of the U-TOC, and records voice data as audio data therein.
Further, in the reproducing apparatus, the areas in which the program to be reproduced is recorded are discriminated by means of the U-TOC, and the reproducing action is made by access to the areas.
Incidentally, in the recordable disc media such as a magneto-optical disc, the random access can be performed extremely easily as compared with tape-like recording media such as a DAT (Digital Audio Tape) and a cassette tape. Accordingly, for example, one program is not necessarily required to be recorded on a continuous segment (the word "segment" means a track portion in which a physically continuous data is recorded), and may be discretely recorded on a plurality of segments. This is disclosed in, for example, U.S. patent application Ser. No. 945,488 filed on Sep. 16, 1992 (now issued as U.S. Pat. No.5,388,903).
In particular, in such a system the data read out of a magneto-optical disc is once stored in a buffer RAM with a high speed writing rate and the read-out is performed from the buffer RAM with a low speed read-out rate. The data read out of the buffer RAM is demodulated as a reproducing audio signal. In this way, even if the read-out of the data from the magneto-optical disc is temporarily interrupted by access between segments, the reproducing sound according to the reproducing signal can be outputted without interruption. This is disclosed in, for example, U.S. Pat. No. 5,214,631.
Accordingly, by repeating the recording/reproducing action in segments and a high access action (access action completed within the reproducible time due to the data storage amount generated by the difference between the writing rate and the reading rate in the buffer RAM), even if the track for one program is physically divided in a plurality of segments, there arises no problem in recording/reproducing the program.
For example, as shown in FIG. 1, a first music and a second music are continuously recorded in segments T1 and T2, respectively, and further, a fourth music and fifth music may be respectively recorded so as to be divided on the tracks as shown in segments T4(1)-T4(4) and T5(1)-T5(2). (In addition, FIG. 1 is a schematic representation. In actual practice, one segment is typically recorded in a spiral or radial manner extending from several tracks to several hundreds tracks.)
When the recording and the erasing of the program are repeated for the magneto-optical disc, empty areas tend to be irregularly generated on tracks due to the difference in the playing time of the program to be recorded or the playing time of the erased program; however, by executing the discrete recording described above, it is possible to record the program longer the erased program by utilizing the erased portion, and hence to eliminate the waste of the data recording areas by repeating the recording/erasing.
In addition, the data to be recorded is not necessarily limited to the "program", and may include voice signals. In this embodiment, however, the data block continuous in its content (recording data unit) will be expressed as the "program".
Of course, for such disc media, the audio-recording and the reproducing must be made as follows: namely, at the time of recording, the audio-recording must be continued while giving access to a plurality of segments as recordable areas; and at the time of reproducing, the access to the segments must be performed such that one program is reproduced so as to be correctly continued. Accordingly, the data for linking the segments (for example, T4(1) to T4(4)) and the data indicating the recordable area are kept as the U-TOG information. The U-TOG information is rewritten for each recording action or erasing action as described above. The recording/reproducing apparatus reads this U-TOC information and gives access of the head, thereby controlling the recording/reproducing action to be suitably performed.
Incidentally, when the program data is recorded, in the case that the recordable areas of a plurality of segments exist and the recording is carried out over a plurality of segments, if these segments (recordable areas) are physically apart from each other, there occurs a problem that the interruption of the reproduced sound is generated or the shock-proof function is deteriorated in reproducing.
The reason for this is that a prolonged time is required for the access between the segments for reproduction. During this time, the read-out of the data from the disc is interrupted. Namely, while the output of the reproduced sound is performed insofar as the reproducing data is stored in the buffer RAM even in the access period in which the read-out of the data from the disc is interrupted, the reproducing data in the buffer RAM becomes empty when the access takes a lot of time, thus causing the interruption of the sound.
Further, in the case that the tracking is shifted by vibration, since the data is stored in the buffer RAM by a content for a specified time, the reproduced sound generated from the reproducing signal can be outputted without interruption for a time required to recover proper tracking. However, when the access takes a lot of time and thereby the data stored in the buffer RAM is consumed, there occasionally occurs a case that the sound cannot be continuously outputted for the time required to recover the tracking. In other words, the shock-proof function is deteriorated.